1. Field of the Invention
The present invention relates to a method and to a device for rapid high-power refrigeration.
2. Description of the Related Art
It is known to produce heat or refrigeration in installations based on liquid/gas phase changes or reversible sorptions between a gas, called the working gas, and a liquid or solid sorbent. A reversible sorption may be an absorption of a gas by a liquid, an adsorption of a gas on a solid, or a reaction between a gas and a solid. A reversible sorption between a sorbent S and a gas G is exothermic in the synthesis direction S+G→SG, and endothermic in the decomposition direction SG→S+G. In a liquid/gas phase change of G, condensation is exothermic and evaporation is endothermic. These reversible phenomena may be represented on the Clausius-Clapeyron plot by their equilibrium line:
            ln      ⁢                          ⁢      P        =          f      ⁡              (                              -            1                    /          T                )              ,            more      ⁢                          ⁢      precisely      ⁢                          ⁢      ln      ⁢                          ⁢      P        =                  -                              Δ            ⁢                                                  ⁢            H                    RT                    +                        Δ          ⁢                                          ⁢          S                R            P and T being the pressure and temperature respectively, ΔH and ΔS being the enthalpy and the entropy, respectively, of the phenomenon (decomposition, synthesis, evaporation, condensation) involved, and R being the ideal gas constant. The endothermic step may be profitably employed in an installation of this type to freeze various products (especially water for obtaining ice) or for the production of cold water.
Thus, EP-0,810,410 describes a device comprising a reactor that is the site of a thermochemical reaction or of a solid-gas adsorption involving a gas G, and a chamber connected to the reactor via a line provided with a valve and operating alternately as evaporator and as condenser for the gas G. The reactor includes means for heating its contents and means for extracting the heat of the exothermic synthesis reaction, these means being formed either by a heat exchanger or by the increase in thermal mass of the reactor. The reactor is arranged in such a way that, with its contents, it has a thermal mass sufficient to absorb the heat produced during the exothermic reaction. The method of managing this device consists in bringing the evaporator/condensor into communication with the reactor when the evaporator/condenser is filled with the working gas in liquid form, this having the effect of cooling the evaporator/condenser by evaporation, and then in operating the means intended to heat the solid so as to deliver and condenser the gas in the evaporator/condenser. The operation of the means intended to reheat the solid in the reactor starts before the previous step has been completed. However, in this device, the cycle times are relatively long owing to the fact that the regeneration of the device takes place at a high temperature Th and the cooling of the reactor takes place at the ambient temperature To. Consequently, the reactor experiences a relatively large thermal amplitude between the regeneration temperature and the ambient temperature, resulting in a low performance factor. Moreover, since the exothermic condensation takes place in the same chamber as the endothermic evaporation, the thermal amplitude of the evaporator/condenser chamber is high, leading to long cycle times and reducing the performance.
WO-97/40328 describes a refrigeration and/or heat production device comprising two reactors in thermal contact, alternately connected either to a condenser or to an evaporator, respectively. In this device, refrigeration takes place from an evaporator that releases a working gas G which, during the regeneration step, is sent into a condenser.
EP-0,580,848 describes a refrigeration and/or heat production device in which refrigeration takes place from an evaporator that releases the working gas G. The device comprises, on the one hand, an evaporator and a separate condenser and, on the other hand, two sets of two reactors each, the two sets operating in a reversed and alternating manner in order to ensure continuous refrigeration. During the refrigeration phase in one of the sets, the reactors of said set are connected to the evaporator, while, at the same time, the reactors of the second set are connected to the condenser and operate in regeneration phase. Next, the connections are reversed and the reactors of the first set are connected to the condenser for the regeneration phase, whereas the reactors of the second set are connected to the evaporator for the refrigeration phase. The evaporator and the condenser are designed to be able to exchange heat with their environment, thereby reducing the refrigeration efficiency. The devices of the two aforementioned documents of the prior art always comprise two reactors that operate in phase opposition, one of the reactors being connected to the condenser while the other reactor is connected to the evaporator. The evaporator and the condenser are therefore continually in operation and are alternately isolated and connected to one of the reactors.
EP-0,382,586 describes a refrigeration device comprising an evaporator and a condenser for the working gas, and two reactors that are the sites of different reversible phenomena involving the same working gas. The reactors operate alternately. A given reactor is connected to the evaporator when it is in synthesis (refrigeration) phase and connected to the condenser when it is in decomposition (regeneration) phase. The temperature of the condenser is above that of the evaporator. The working gas condensed in the condenser serves to feed the evaporator. The evaporator and the condenser are designed to be able to exchange heat with their environment, thereby reducing the refrigeration efficiency.
The refrigeration methods of the prior art require a particular and relatively complex method of control owing to the difficulty in controlling the connections between the various components of the device. Furthermore, the devices of the prior art for the production of ice for domestic use are essentially systems based on the mechanical compression of a vapor, which use a refrigerant fluid. In general, a simple removable ice tray is placed in a refrigerated compartment maintained at a temperature of between −10° C. and −22° C. The water contained in the ice tray then freezes over several hours (typically around 4 to 5 hours for about 200 g of water) by heat exchange with the air in the refrigerated compartment. The pieces of ice are preserved in said refrigerated compartment for periods that may range from a few days to a few tens of days, causing their quality to degrade, or even contaminating the pieces of ice with mineral inclusions and/or pollutants, so that ultimately the ice is unsuitable for consumption.